Melting and Crystallization of Metallocene Polypropylenes

ABSTRACT The melting and crystallization behaviors of metallocene polypropylene (mPP) were investigated using simultaneous synchrotron radiation small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray scattering (WAXS) techniques in this work. It was found that both γ and α forms can be detected after crystallization from the melt at atmospheric pressure. The in situ simultaneous SAXS/WAXS investigations displayed that the γ form melts faster than the α form before heating to 160°C and more slowly after heating to 160°C during the melting of the mPP after isothermal crystallization. Both of the crystals form simultaneously during non‐isothermal crystallization, but they crystallize in different ways during isothermal crystallization. The evolution of SAXS results, including the scattering intensity and structure‐related q value, indicates a possible segment cluster aggregation in the mPP. Therefore, a possible crystallization process was proposed to understand the formation of the γ crystal in mPP.